Previously, most rolling mills for flat products have been two high and four high rolling mills, as shown in FIG. 1 and FIG. 2. However technical problems, such as control of thickness in a widthwise direction (plate crown) and flatness uniformity (plate shape), have occurred in these mills. As a means to resolve these technical problems, rolling mills with various roll equipment of bending, shifting and crossing and the like have been developed.
Each of these mills is equipped with an effective controlling device and technology that has already been adopted in various rolling mills, but even if these mills are used, uniform distribution of the rolling load between a rolled material and work-roll cannot been obtained, thereby making it difficult to estimate precisely the crown and shape of the product after rolling.
It is possible to estimate plate crown and plate shape based on such data as rolling load, plate width, plate thickness, the crown and shape before rolling which may be measured or estimated, and the operating conditions for crown and shape control device of the rolling mill.
In this case, however, the accuracy of estimation is limited, so that recent requirements for extreme precision must depend on feedback regulations with a thickness profile meter and a plate shape meter set behind a rolling stand.
The problem with the feedback regulation is the loss of time, which requires more time for rolled material to approach a measuring device from an outlet. Therefore it is difficult to increase a regulation gain, and it is impossible to correspond with high frequency disturbances. Furthermore, generally speaking, the capability of the regulating device for the plate crown and shape is limited within parabolic or quartic distribution with respect to an axis of a plate widthwise direction.
As regards the above mentioned method, a shape regulation method using an eccentric ring in a divided support-roll is adapted in a cluster rolling mill (generally called As- U mechanism), and is capable of regulating a complicated pattern in a widthwise direction. However, even if a profile of the divided support-roll can be obtained in a rolling mill with the As- U mechanism, it is difficult to detect a rolling load distribution and attain a precise work roll bend and roll flattening, which affects the plate profile.
Further, in such a cluster rolling mill, it is possible to devise a mechanism for a rolling mill that detects a rolling load, but even in this case, it is impossible to measure the distribution of the rolling load in a widthwise direction so that the same problems as in the above case will occur.
In Japanese Unexamined Patent Publication No. 57-68208, it is proposed that a work-roll is supported by a support beam through a liquid, and the liquid portion is divided by plural chambers in an axiswise direction. Owing to an increase in the number of divided chambers, it becomes possible to regulate a work-roll bend flexibly, and it is possible to estimate load distribution operating between a work-roll and a support beam through a liquid pressure and load area of each chamber, thereby making it possible to estimate, approximately, load distribution between a rolled material and a work-roll.
However, a problem involving capacity limitation and sealing technique occurs in that excessive impact loads, or compressive stress increases through chambers or the like are not tolerated and a large amount of bending of a work-roll cannot be realized because it induces leakage of the liquid through the sealing device.
A large amount of bending of a work-roll is needed in the following situation, which inevitably arises in a usual rolling operation.
1 to compensate a profile change of work-roll by abrasion and heat expansion,
2 to correct a crown ratio of plate crown/plate thickness during rolling that is different from a crown ratio intended originally,
3 to produce a plate that has a non-uniform thickness distribution prescribed in a widthwise direction.
No prior art has disclosed a rolling mill that, owing to control of a plate crown and shape, can freely regulate a work-roll bend, according to prompt estimation of a plate crown and plate shape based on rolling information obtained by itself.
An object of the invention is to provide a rolling mill for flat products that can freely regulate a plate crown and shape by bending a work-roll according to prompt estimation of a plate crown and shape based on-rolling information obtained by itself.